According to a conventionally known linear motion guide unit, a retainer plate has a light structure and can be simply and easily held to end caps to thereby reduce the size of a slider. The linear motion guide unit is composed of a guide rail, and the slider moving on the guide rail via rollers. The slider has a carriage and end caps fixed to the respective opposite ends of the carriage. The rollers located on the raceway surface side of the carriage are retained to the carriage by the retainer plate. The retainer plate is fixed to the carriage by screwing fastening bolts inserted through respective insertion holes formed in the carriage into respective nuts disposed at the back of the retainer plate. The retainer plate is composed of a pair of flat plate portions formed by bending a thin plate along its longitudinal direction in such a manner as to have a V-shaped section. The pair of flat plate portions are formed to be greater in length than the carriage, and opposite end portions thereof are fixedly fitted into respective engagement grooves formed in the end caps. The flat plate portions guide the end surfaces of the rollers rolling on the upper and lower raceway surfaces of the carriage to thereby retain the rollers on the raceway surfaces. In order to hold the retainer plate to the slider, the carriage has the insertion holes formed therein, and the bolts are screwed into the respective nuts provided on the back of the retainer plate (see, for example, Japanese Patent Application Laid-Open No. 2014-234858).
According to another conventionally known linear motion guide unit, retainer means for retaining cylindrical rollers is snap-on fixed to a slider to thereby increase the rated load of the slider. In the linear motion guide unit, a retainer plate is disposed between the cylindrical rollers disposed on an upper raceway surface of the carriage and the cylindrical rollers disposed on a lower raceway surface of the carriage. A holder portion of a fixing band is engaged with an engagement groove of the retainer plate and with engagement grooves of end caps. Engagement beaks at the ends of bend portions of the fixing band are engaged with respective engagement holes formed in the end caps. The retainer means for retaining the cylindrical rollers is incorporated in the slider and retains the cylindrical rollers to a load-carrying race formed by a guide rail and a carriage (see, for example, Japanese Patent Application Laid-Open No. H07-91446).
Meanwhile, conventionally, in a linear motion guide unit which uses rollers as rolling elements, in some cases, the axes of rollers rolling in the load-carrying race are inclined with respect to the moving direction. The inclined rolling rollers may cause the occurrence of skew in which the rollers roll while generating sliding friction. In conventional linear motion guide units, a beak of the retainer plate retains the rollers, or rolling elements, to the raceway surface of the carriage while a guide surface of the retainer plate guides the end surfaces of the rollers, thereby preventing the occurrence of skew. However, in order to smoothly circulate the rollers, a small gap must exist between the end surfaces of the rollers and the guide surface. According to conventional measures to prevent the occurrence of skew, components which constitute a circulating circuit are manufactured with high precision for reducing the gap between the rollers and the guide surface. However, such measures are costly. Therefore, inexpensive measures to prevent the occurrence of skew have been desired.